The present invention relates to distributor ducts, and controls for their operation and associated components, which deliver gaseous or liquid fluid to the fluid ports of a fluid powered mechanism, and more particularly, to a distributor duct for controlling the input and output under pressure of fluid to a plurality of pneumatic or hydraulic cylinders which are used to control the reciprocating movement of valve pins which control the flow of molten plastic into a mold cavity in an injection molding machine/apparatus.
The present invention comprises a distributor for delivering an actuator operating fluid, e.g. oil/hydraulic or gas/air, via a common duct or ducts to a plurality of fluid driven cylinders in an injection molding machine and two or more control mechanisms which control the operation of two or more of the cylinders such that the cylinders and their associated valves can be independently controlled to deliver the flow of molten plastic at differing time and rates to one or more mold cavities. Operation or actuation of the control mechanisms for the cylinders is preferably controlled via a computer program which executes an algorithm using parameters such as a condition of the plastic melt flow in the nozzles or the mold cavity or a hotrunner which supplies melt flow to the nozzles. The algorithm may utilize other parameters such as the position of a valve pin or injection screw or a condition of the machine, hotrunner, mold or component thereof. Typically the pressure of the plastic melt in the nozzles, mold cavity or hotrunner is utilized as an input variable to the control algorithm. The distributor is preferably readily attachable to and detachable from the cylinders such that a sealed connection can be readily effected between fluid delivery channels provided in the distributor and fluid feed bores provided in the cylinders. The distributor is structurally independent of the cylinders which have self-contained fluid sealable piston bores and are spaced from the heated components of the machine.
The disclosure of copending U.S. application Ser. No. 08/972,277, for Apparatus For Controlling Plastic Melt Flow In Injection Molding Machines, filed Nov. 18, 1997 by the same inventor is incorporated herein by reference. This application claims the priority benefit of prior filed co-pending provisional application Ser. No. 60/076,612 filed Mar. 3, 1998. The disclosure of copending U.S. application Ser. No. 09/063,762 entitled xe2x80x9cManifold System Having Flow Controlxe2x80x9d filed Apr. 21, 1998 assigned to the same effective assignee is also incorporated herein by reference.
In accordance with the invention there is provided, in an injection molding machine, an apparatus for automatically controlling the movement of two or more valve pins wherein each valve pin is driven by a separately controlled fluid driven cylinder each cylinder being mounted on a heated manifold and being interconnected to a separate valve pin for effecting reciprocal movement of the valve pin wherein the reciprocal movement of the valve pin controls the flow of molten plastic being delivered through a nozzle which delivers molten plastic to a gate of a mold, the apparatus comprising: a fluid distributor housing having one or more fluid flow channels which commonly delivers a drive fluid to each of the cylinders, each of the cylinders having a piston slidably mounted within a bore of an enclosed cylinder housing for reciprocal fluid driven movement of the piston within the bore of the cylinder housing; each cylinder having a first and a second fluid input port to the bore of each cylinder housing, the first and second fluid input ports being selectively connectable to a fluid flow channel of the fluid distributor housing; and, a drive fluid controller associated with each cylinder, each controller being controllable to selectively connect one or the other of the first and second fluid input ports of each cylinder to a fluid flow channel.
Each controller is preferably interconnected to a common computer program which controls operation of each controller according to a predetermined algorithm. The algorithm typically controls the operation of the controllers according to one or more of a sensed condition of the molten plastic, a selected position of a valve pin and a selected condition or position of the injection molding machine.
Further in accordance with the invention there is provided an apparatus for separately controlling the movement of two or more valve pins wherein each valve pin is driven by a separate fluid driven cylinder each separate cylinder being mounted on a heated manifold and being interconnected to a separate valve pin for effecting reciprocal movement of the valve pin wherein the reciprocal movement of the valve pin controls the flow of molten plastic being delivered through a nozzle which delivers molten plastic to a gate of a mold, the apparatus comprising:
a fluid distributor housing having a fluid flow channel which commonly delivers a drive fluid to each of the cylinders, each of the cylinders having a piston slidably mounted within a bore of an enclosed cylinder housing for reciprocal fluid driven movement of the piston within the bore of the cylinder housing;
each cylinder having a first and a second fluid input port to the bore of each cylinder housing, the first and second fluid input ports being selectively connectable to the fluid flow channel of the fluid distributor housing;
a drive fluid switch associated with each cylinder, each switch having a drive fluid flow connector and a drive fluid seal, the connector of each switch being connectable to one of the first and second fluid input ports of each cylinder while the seal of each switch is simultaneously operative to act on the other of the first and second fluid input ports of each cylinder.
Preferably, each switch is independently controllable to switch the connection of the connector and the seal between the first and second fluid input ports of each cylinder. Each switch is typically interconnected to an electrically driven mechanism, the electrically driven mechanism driving the switch between a first position connecting the first fluid input port to the fluid flow channel and a second position connecting the second fluid input port to the fluid flow channel.
Preferably, the electrically driven mechanisms are interconnected to a common computer program which controls the drive of each electrically driven mechanism according to a predetermined algorithm. The algorithm is typically configured to control the drive of the electrically driven mechanisms according to at least one of a selected condition of the molten plastic, a selected position of the valve pin and a selected condition or position of the injection molding machine.
The fluid distributor housing typically includes first and second fluid flow bores sealably matable with the first and second fluid flow ports respectively of each cylinder. Most preferably a compressible member is sandwiched between each fluid flow bore of the distributor housing and each complementary fluid input port of the cylinders such that fluid flow between each fluid flow bore and each complementary fluid input port is fluid sealed. Each cylinder is preferably configured to have a selected widened external mounting surface and wherein the distributor duct housing has complementary selected widened external surface areas for mating with the selected mounting surfaces of the cylinders.
Most preferably the fluid distributor housing is readily attachable to and detachable from each of the cylinders, the cylinders are mounted a spaced distance on and from an external surface of the heated manifold and the cylinders are interconnected to the valve pins at a position external to the bores of the enclosed cylinder housings. The fluid distributor housing may comprise a heat conductive material, the fluid distributor housing being mounted on the cylinders such that the selected widened mounting surfaces of the cylinders are mated in compressed contact with the complementary selected widened surface areas of the fluid distributor housing, heat being readily conductible from the cylinders to the fluid distributor housing through the mated surfaces.
The fluid distributor housing may comprise at least a portion of a wall of the cylinder housing which sealably encloses the bore of the cylinder or the fluid distributor housing may comprise a structure independent of the cylinder housing which is readily attachable to and detachable therefrom.